OLYMPIA, Wash. (AP) - Washington voters are set to narrow their choices in dozens of races, including governor and U.S. Senate. Here are some things to know ahead of Tuesday’s primary:

HOW MANY CANDIDATES ARE ON THE BALLOT?

More than 670 candidates are vying for federal, statewide, legislative, county, judicial and local offices, according to the secretary of state’s office. The races include U.S. Senate, governor, lieutenant governor, state auditor, office of superintendent of public instruction and state Supreme Court.

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HOW DOES WASHINGTON’S ‘TOP 2’ PRIMARY WORK?

The top two vote-getters in each race advance to the November election, regardless of party. That means in some contests, two Republicans or two Democrats could end up on the general election ballot. Also, voters don’t have to declare a party affiliation and can choose among all candidates on one, consolidated ballot.

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WHAT’S THE MOST CLOSELY WATCHED RACE?

The lieutenant governor’s race drew 11 contenders, including three Democratic state senators, after current Lt. Gov. Brad Owen announced his retirement. He has held the office for two decades.

The two candidates who have raised the most money - Sens. Cyrus Habib and Steve Hobbs - are Democrats. If they advance to the general election, it will be the first time two Democrats have faced off in a statewide race since Washington launched the top two primary system in 2008, according to the secretary of state’s office. Same-party opponents have emerged in legislative and congressional races but never in a statewide contest.

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WHAT ABOUT OTHER OPEN SEATS?

Four other open statewide seats - auditor, lands commissioner, treasurer and superintendent of public instruction - have drawn several candidates.

The 7th Congressional District, which includes Seattle, also is drawing attention. It is an open seat after Jim McDermott decided to retire after serving 14 two-year terms in Congress. The race has drawn nine candidates, including Democratic Sen. Pramila Jayapal, Democratic Rep. Brady Walkinshaw and Metropolitan King County Councilman Joe McDermott, also a Democrat.

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ARE ALL OF THE LEGISLATIVE RACES COMPETITIVE?

No, most aren’t. In 78 of the 124 legislative races on the ballot, there’s no real contest in the primary. Twenty-seven contests are unopposed, and in 51 seats, only two candidates are running; they will all automatically advance to the November ballot.

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HOW MANY VOTERS ARE EXPECTED?

The secretary of state’s office has predicted turnout for the primary will be at about 41 percent. But as of Monday morning, only about 14 percent of the 4.1 million ballots sent to voters had been returned. Ballots must be either postmarked or dropped off at a local drop box by Tuesday.